Globally, women in established relationships remain at risk for unintended pregnancy and sexually transmitted infections (STIs), including HIV. In Vietnam, the location of the proposed research, unmet need for contraception is substantial as reflected in the nation's high abortion ratio. Married women account for about one-third of HIV cases in Vietnam, and among this group, most were exposed to the virus through sexual activity with their husband. Despite recent advancements in biomedical interventions for HIV prevention, condoms will remain a crucial component of reproductive health interventions for some time to come. Sustained condom use, however, is notoriously difficult to achieve. A key barrier to the consistent use of condoms is their effect on sexual pleasure. Although sexual pleasure is a primary motivation for engaging in sex and is an integral part of overall sexual health, most programs to improve sexual health operate within a pregnancy and disease-prevention paradigm. A new condom, CSD500, containing an erectogenic drug was developed for use among healthy couples to improve sexual pleasure by increasing penile firmness, size and erection duration. The overall objective of the proposed two-arm randomized trial is to test whether promoting the novel condom CSD500 for improved sexual pleasure results in couples having less unprotected vaginal sex. We will measure the occurrence of unprotected vaginal sex by testing women's vaginal fluid for the presence of prostate-specific antigen (PSA), an objective, biological marker of recent semen exposure. The project has three specific aims: Aim 1. To evaluate whether CSD500 provided to improve sexual pleasure, as compared to the standard condom, results in less semen exposure among women in an established relationship. Aim 2. To determine whether CSD500 provision increases men and women's reports of sexual pleasure, as measured using a validated scale. Aim 3. To identify correlates of semen exposure, measured by PSA positivity, which could provide insight into subgroups of women who fail to use condoms consistently. To accomplish these aims, we will randomize 500 adult, heterosexual, monogamous couples in Thanh Hoa province, Vietnam to receive either CSD500 for sexual pleasure or the standard condom currently provided only for pregnancy and disease prevention to patients during routine care. We will interview female participants at enrollment and after 2, 4, and 6 months and their male partners at the 6-month visit. We will sample vaginal fluid from female participants at all visits to test for the presence of PSA. The proposed study is significant because the results could support a transformative approach of promoting condoms for sexual pleasure in order to prevent unintended pregnancy and HIV/STIs.